1. Field of the Invention
The invention relates to a flexible electrical line which in a core has at least one sensor element and leads consisting of insulated electrical conductors which are surrounded by a common outer casing of insulation material, in which the sensor element consists of respectively two leads each having an insulated electrical conductor with a tension-proof central element which, together with two filler strands consisting of insulation material are stranded into a unit which is surrounded by a banding of insulation material, over which a casing is arranged (DE 10 2006 015 878 A1).
2. Description of Related Art
Lines of this type can be used, for example, in large crane systems which move around in a harbor area, for example, along a rail system. The line is wound onto a coil which is rotatably mounted, for example, on a crane. It is coiled on and off when loads or the entire crane are moved. During this procedure, tension loads may act on the line, particularly when a change of the direction of rotation of the coil occurs, and during start-up and/or deceleration. The tensile loads may also be detected and may be indicated by a sensor element contained in the line and displayed.
The known flexible line according to the above-mentioned DE 10 2006 015 878 A1 has a centrally arranged sensor element whose capacity values change in dependence on the tensile load of the line. These changes can be measured and used for influencing the drive of the coil onto which the line is being wound, in order to achieve a reduction of the load acting on the line. In this line, two layers of control leads are stranded onto the sensor element, wherein the control leads are surrounded by an outer casing of insulation material. For example, by means of the control leads, signals can be transmitted to a crane or for the drive of the coil onto which the line is being wound. In the same manner, it is possible to supply through the control leads a voltage of at most 1 kV to a crane installation. The sensor element has a pair of leads composed of two insulated conductors. Each lead thereof consists of a core element of a tension-proof synthetic material, a layer of copper wires stranded onto the core element, and a layer of a compressible insulation material which surrounds the layer of copper wires. The pair of leads is stranded together with two filler strands which consist of polyethylene terephthalate yarns. The sensor element is surrounded by a casing of synthetic material.